WO2017085975A1

WO2017085975A1 - Replaceable-cutting-edge rotary cutting tool and insert

Info

Publication number: WO2017085975A1
Application number: PCT/JP2016/074240
Authority: WO
Inventors: 康博木内; 由幸小林; 中見川　崇夫; 史彦稲垣; 裕貴林
Original assignee: 三菱日立ツール株式会社
Priority date: 2015-11-16
Filing date: 2016-08-19
Publication date: 2017-05-26
Also published as: EP3378589A4; KR102021271B1; KR20180069016A; US20200254529A1; EP3378589B1; CN108290231B; CN108290231A; EP3378589A1; US10799956B2

Abstract

In this replaceable-cutting-edge rotary cutting tool (6), a cutting edge part (4) of an insert (5) is provided with a bottom cutting edge (11), a radiused-corner cutting edge (13), and a chamfered surface (15). The radial-direction rake angle (δ) of the radiused-corner cutting edge (13) has a negative value for the entire blade length of the radiused-corner cutting edge (13), and the radial-direction rake angle (δ) has the smallest value at the intermediate part located between a pair of boundary points (P, Q) of the radiused-corner cutting edge (13).

Description

Replaceable blade cutting tool and insert

The present invention relates to a blade-tip-exchange-type rotary cutting tool equipped with a cutting insert suitable for side finishing of a work material, and an insert.
This application claims priority based on Japanese Patent Application No. 2015-223958 filed in Japan on November 16, 2015, the contents of which are incorporated herein by reference.

Conventionally, a square type solid end mill has been used to finish a bottom surface serving as a processing reference surface or a side surface perpendicular to a horizontal surface on a work material such as a mold. However, in machining with a long tool protrusion (L / D is 4 or more), the machining accuracy is difficult to obtain due to the tilting of the tool. Of the “L / D”, the L value is the length in the direction of the rotation center axis of the tool, and the D value is the diameter of the rotation locus of the tool cutting edge.
For the solid type, for example, the tool itself is very expensive when the outer diameter is φ10 mm or more. For long tool overhang (L / D is 4 or more), a blade end replaceable radius end mill is used. Is done. In order to obtain machining accuracy, it is necessary to perform machining under reduced cutting conditions so as to suppress the occurrence of chatter vibration and to prevent chipping and chipping from occurring on the cutting edge. Note that “reducing the cutting condition” means, for example, that cutting conditions such as a cutting amount and feed are suppressed to a low value.
For this reason, various proposals have been made regarding the cutting edge shape of the blade end replaceable radius end mill.

Patent Document 1 (Japanese Patent Application Laid-Open No. 8-281513) discloses a blade-tip-replaceable end mill in which an insert can be detachably held by a V-shaped slit at the tip of a tool body. An outer peripheral blade formed in the axial direction from the tip apex angle of the main body, a bottom blade positioned substantially perpendicular to the outer peripheral blade, and a corner composed of a substantially circular arc in contact with the outer peripheral blade and the bottom blade at the bottom blade corner. A blade-tip-replaceable end mill having an R blade and a non-gash portion with a width of 0.1 to 1 mm parallel to the outer peripheral blade with a gash angle of the bottom blade of 30 to 45 ° is described.

In Patent Document 2 (Japanese Patent No. 5744235), a bottom cutting edge that exists at the tip of the tool body and an outer peripheral cutting edge that exists at the outer periphery of the tool body are formed. There is described a radius end mill in which a gap is connected by a corner R cutting edge, a chip discharge groove is provided behind the rake face of the outer peripheral cutting edge, and a corner gash adjacent to the corner R cutting edge is formed. The corner gash is provided on a corner R cutting edge other than the boundary between the corner R cutting edge and the bottom cutting edge and the boundary between the corner R cutting edge and the outer peripheral cutting edge, and is in contact with the corner gash. Patent Document 2 describes that the axial rake at the end on the bottom cutting edge side is set to 5 to 20 °.

In the radius end mill described in Patent Document 3 (Japanese Patent No. 5267556), the chip discharge groove provided on the outer periphery of the end portion of the end mill body or the wall surface facing the rotation direction of the end of the gasche provided on the tip portion of the chip discharge groove is provided. The corner face connecting the bottom cutting edge and the outer peripheral cutting edge includes a convex arcuate corner edge, and the corner edge is a positive edge. The cutting edge that has a cutting edge inclination angle and is located on the side ridge side of the rake face is inclined to the rear side in the end mill rotation direction from the bottom blade side toward the outer peripheral blade side, and the rear side in the end mill rotation direction Is formed in a twisted surface shape that gradually increases from the corner blade toward the center of the convex arc formed by the corner blade.

In Patent Document 4 (Japanese Patent Application Laid-Open No. 2011-20192), the rake angle of the rake face of the bottom blade is a negative angle, and the rake angle of the rake face of the corner R and the rake face of the outer peripheral cutting edge is also negative. A solid-type twisted-blade radius end mill with an angle of?

JP-A-8-281513 Japanese Patent No. 5744235 Japanese Patent No. 5267556 JP 2011-20192 A

In Patent Document 1, a slit extending in the axial direction is provided at the distal end portion of the holder body, and a chip having a cutting edge is sandwiched by the leading edge protruding from the slit by the slit, and is emitted from the top apex angle of the cutting edge chip. An outer peripheral blade in the axial direction, a bottom blade positioned substantially perpendicular to the outer peripheral blade on a diagonal line including the center of the axis from the apex angle generated by the outer peripheral blade, and an approximately 1/4 arc in contact with the outer peripheral blade and the bottom blade at the bottom blade corner There is described a throw-away end mill characterized in that a cutting edge tip provided with a pair of corner radius blades is provided.
However, the end mill of Patent Document 1 has room for improvement in improving the biting of the outer peripheral cutting edge in the side finishing of the work material and extending the tool life in the bottom finishing.

In Patent Document 2, a cutting edge shape in which a corner gash is provided in a corner R blade is studied and described. In the corner R cutting edge in the vicinity of the outer peripheral cutting edge, there is a step or a corner at the joint with the outer peripheral cutting edge. In addition to controlling what can be done, it improves the ability of cross feed processing by improving the sharpness. Further, Patent Document 2 discloses that the axial rake in the vicinity of the bottom blade is small, there is no step on the rake face, and the outflow of chips is not hindered. Are listed.
However, the end mill of Patent Document 2 has room for improvement in the biting of the outer peripheral cutting edge in the side finishing of the work material and the tool life in the bottom finishing.

In Patent Document 3, with respect to the corner R cutting edge connected from the bottom cutting edge side to the outer peripheral cutting edge side, it is possible to suppress a significant change in the right-angle rake angle along the corner R cutting edge and further suppress a change in the cutting edge inclination angle. The radius and mill cutting edge shape, which exhibits more stable cutting performance by ensuring dischargeability, has been studied and described.
However, the end mill of Patent Document 3 has room for improvement in improving the biting of the outer peripheral cutting edge in the side finishing of the work material and extending the tool life in the bottom finishing.

In Patent Document 4, the rake angle of the rake face of the bottom blade is a negative angle, and the rake angle of the rake face of the corner R and the rake face of the outer peripheral cutting edge is also set to a negative angle. A solid-type twisted-blade radius end mill that improves the durability of the tool by improving the chip evacuation performance while increasing the fracture resistance of the blade is described.
However, the end mill of Patent Document 4 has room for improvement in the biting of the outer peripheral cutting edge in the side finishing of the work material and the tool life in the bottom finishing.

The present invention improves the cutting performance particularly when machining a long tool protrusion (for example, L / D is 4 or more) when finishing the bottom surface serving as a machining reference surface or a side surface perpendicular to a horizontal surface on a work material such as a mold. Another object of the present invention is to provide a blade-tip-replaceable rotary cutting tool and an insert excellent in dimensional accuracy in side finishing perpendicular to a horizontal plane in addition to the finishing dimensional accuracy of the bottom surface of the work material.

One aspect of the present invention is a blade-tip-exchange-type rotary cutting tool in which an insert having a cutting edge portion is detachably attached to a mounting seat provided at a distal end portion of a tool main body, and the mounting seat is formed of the tool main body. A slit-like insert fitting groove formed to extend in a radial direction perpendicular to the rotation center axis including the rotation center axis of the tool and the insert inserted into the insert fitting groove are fixed to the distal end portion. And a cutting edge portion of the insert extends along the radial direction, a rake face of the outer cutting edge, and a radial direction. Connecting the bottom cutting edge, the rake face of the bottom cutting edge, the radial outer end of the bottom cutting edge and the tip of the outer peripheral cutting edge in the rotational center axis direction, and the outer peripheral side of the tip of the tool body Arc shape that protrudes toward Of the formed corner R cutting edge, the rake face of the corner R cutting edge, the rake face of the corner R cutting edge, and the rake face of the bottom cutting edge, at least a portion located outside in the radial direction. Including a chamfered surface, a chip discharge groove formed on the base end side of the rake face of the bottom cutting edge in the direction of the rotation center axis, and a chip discharge formed on the inner side of the rake face of the outer peripheral cutting edge in the radial direction. A twist angle of the outer peripheral cutting edge has a positive value, and an axial rake angle of the corner R cutting edge at a boundary point between the corner R cutting edge and the outer peripheral cutting edge is negative. The axial rake angle of the corner R cutting edge at the boundary point between the corner R cutting edge and the bottom cutting edge has a negative value, and a predetermined point on the corner R cutting edge And a reference plane including the rotation center axis The angle at which the rake face of the corner R cutting edge is inclined with respect to the reference plane in a virtual plane that is vertical and includes a virtual straight line passing through the arc center point of the corner R cutting edge and the predetermined point. Is defined as a radial rake angle, and the radial rake angle of the corner R cutting edge has a negative value over the entire length of the corner R cutting edge, and the radial rake angle is The corner has a minimum value in an intermediate portion located between the pair of boundary points among the corner R cutting edges (hereinafter referred to as “the blade-tip-exchangeable rotary cutting tool of the present invention”). ).
An insert according to another aspect of the present invention is characterized by being used in the above-described blade-tip-exchange-type rotary cutting tool (hereinafter referred to as “the insert of the present invention”).

In the cutting edge exchange type rotary cutting tool and insert of the present invention, the axial rake angle of the corner R cutting edge at the boundary point (outermost peripheral position) between the arcuate corner R cutting edge and the outer peripheral cutting edge has a negative value. The rake angle in the axial direction of the corner R cutting edge at the boundary point (the most advanced position) between the corner R cutting edge and the bottom cutting edge has a negative value. That is, the axial rake angle of the corner R cutting edge is a negative angle. Further, the twist angle of the outer peripheral cutting edge has a positive value and is a positive angle.

Since the cutting edge-exchangeable rotary cutting tool and the insert of the present invention have this configuration, the boundary point between the corner R cutting edge and the outer peripheral cutting edge is directed to the tool rotation direction in the circumferential direction around the rotation center axis of the tool. The most protruding point (the most convex point). For this reason, in the side finishing process in which a wall surface (vertical surface, standing wall) perpendicular to the horizontal plane is processed on the work material, the corner R cutting edge and the outer peripheral cutting edge are covered at the boundary point (the most convex point). Cutting of the work material is started by point contact with the work material. Therefore, the biting of the cutting edge on the work material is improved.

Cutting started by point contact from the boundary point expands the cutting range to the corner R cutting edge and the outer peripheral cutting edge as the tool rotates. Since the axial rake angle of the corner R cutting edge is set to a negative angle, the corner R cutting edge has a reverse twisted blade shape. The outer peripheral cutting edge has a positive twisted blade shape. For this reason, of the cutting forces received by the tool from the work material, the cutting force acting in the direction along the rotation center axis (that is, the back component force) is the tip side (cutting edge side) in the direction of the rotation center axis in the outer peripheral cutting edge. In contrast, the corner R cutting edge acts toward the base end side (tool shank side) in the rotation center axis direction.
Thereby, the cutting resistance acting toward the cutting edge side in the outer peripheral cutting edge can be canceled out. Accordingly, it is possible to improve the phenomenon that the tool body is bent by the cutting force applied to the cutting edge in the direction of the rotation center axis (the bending of the tool due to the cutting force can be reduced).

In addition, it is possible to suppress the escape amount of the outer peripheral cutting edge from the work material that affects the dimensional accuracy in the side finishing process perpendicular to the horizontal surface of the work material, and the vertical reference surface from the upper part to the lower part can be reduced. Can be finished with extremely high precision. In addition, since the biting of the outer peripheral cutting edge and the corner R cutting edge on the work material is started by point contact, the occurrence of chatter vibration is reduced, and the effect of stabilizing the processing can be obtained.

The radial rake angle has a negative value over the entire length of the corner R cutting edge. In addition, the radial rake angle is a minimum value in an intermediate portion of the corner R cutting edge located between the pair of boundary points.
Thus, by ensuring that the radial rake angle of the corner R cutting edge at the pair of boundary points is a negative value (negative angle), the edge strength of the corner R cutting edge is sufficiently ensured. Can do.
On the other hand, for example, unlike the present invention, when one or both of the radial rake angles of the corner R cutting edge at the pair of boundary points are positive values (positive angles), the corner R cutting edge It is inconvenient because strength is reduced.

In addition, since the radial rake angle is a minimum value in an intermediate portion between the pair of boundary points of the corner R cutting edge, the boundary point between the corner R cutting edge and the bottom cutting edge among these boundary points. The rake angle in the radial direction at can be made closer to the positive angle side (positive angle side) than the minimum value while being a negative value. Thereby, the sharpness of the boundary point between the corner R cutting edge and the bottom cutting edge can be ensured in the bottom finishing.

Further, from the boundary point between the corner R cutting edge and the bottom cutting edge, along the corner R cutting edge, toward the boundary point between the corner R cutting edge and the outer peripheral cutting edge (specifically, toward the intermediate portion), Radial rake angle decreases. That is, the rake angle in the radial direction increases toward the negative angle side (negative angle side) as it approaches the intermediate portion, and reaches a minimum value (that is, maximum value on the negative angle side) on the intermediate portion. Therefore, the edge strength can be remarkably improved by providing the intermediate portion located between the pair of boundary points at the cutting edge boundary portion for cutting the work hardened layer of the work material. Therefore, it is preferable because the reliability of the cutting edge in the bottom finish processing is particularly high when a work material that is likely to be work hardened or a work-affected layer is formed on the surface of the work material by processing under high efficiency conditions.

As described above, according to the present invention, when finishing a bottom surface serving as a processing reference surface or a side surface perpendicular to a horizontal surface on a work material such as a mold, particularly in processing with a long tool protrusion (for example, L / D is 4 or more). The cutting performance can be improved, and in addition to the finished dimensional accuracy of the bottom surface of the work material, the dimensional accuracy in the side finishing process perpendicular to the horizontal surface can be significantly improved.

Further, in the above-mentioned blade tip exchange type rotary cutting tool, the radial rake angle of the corner R cutting edge at a boundary point between the corner R cutting edge and the bottom cutting edge is determined by the corner R cutting edge and the outer peripheral cutting edge. It is preferable that it is smaller than the radial rake angle of the corner R cutting edge at the boundary point.

In this case, the radial rake angle of the corner R cutting edge at the boundary point between the corner R cutting edge and the bottom cutting edge is greater than the radial rake angle of the corner R cutting edge at the boundary point between the corner R cutting edge and the outer peripheral cutting edge. Since it is enlarged to the negative angle side (negative angle side), it is possible to improve the chipping resistance of the bottom cutting edge and improve the chip discharge and maintain the finished surface with high quality.

In addition, the radial rake angle of the corner R cutting edge at the boundary point between the corner R cutting edge and the outer peripheral cutting edge can be made closer to the positive angle side (positive angle side) while taking a negative value. In side finishing to machine a wall surface (vertical wall) perpendicular to the material, the cutting force in the tool radial direction (horizontal direction) that the tool that cuts into the work material receives from the work material (that is, the feed force) must be kept small. Is possible. Thereby, chatter vibration is suppressed and the machined surface accuracy can be improved.

More specifically, for example, the radial rake angle (true rake angle) at the boundary point between the corner R cutting edge and the bottom cutting edge is α, and the radial rake angle at the boundary point between the corner R cutting edge and the outer peripheral cutting edge ( Radial rake angle α, radial rake angle β, and radial rake angle γ, where β is the true rake angle and γ is the minimum radial rake angle (true rake angle) in the intermediate portion. Are negative values, and when the radial rake angle α value, β value, and γ value are | α |, | β |, and | γ |, respectively, | γ |> | α It is preferable to have a relationship of |> | β |.

The cutting edge boundary that hits the work hardening layer of the work material in roughing or semi-finishing in advance in bottom finishing and side finishing (especially bottom finishing) by having this configuration in the cutting edge exchange rotary cutting tool The radial rake angle of the portion (intermediate portion positioned between a pair of boundary points) can be set to the smallest negative value. This is preferable because the effect of preventing chipping at the boundary of the cutting edge can be remarkably obtained in roughing or intermediate finishing.
On the other hand, when the above-mentioned | γ |> | α |> | β | is not satisfied, the cutting edge boundary portion is easily damaged in the bottom finishing and side finishing (especially bottom finishing). Sometimes.

Further, in the blade-tip-exchange-type rotary cutting tool, an angle at which the virtual straight line projected on the reference plane is inclined with respect to the rotation center axis in the reference plane is defined as a radiation angle, and the radial direction It is preferable that the minimum value of the rake angle is set in a range of 5 ° to 50 ° in terms of the radiation angle among the corner R cutting edges.
The “virtual straight line projected on the reference plane” refers to projecting a virtual straight line perpendicular to the reference plane.

The cutting edge that cuts the work hardened layer of the work material while ensuring the sharpness of the boundary point between the corner R cutting edge and the bottom cutting edge in the bottom surface finishing by having the blade tip exchange type rotary cutting tool having this configuration. The edge strength of the boundary portion (intermediate portion located between the pair of boundary points) can be improved. Therefore, it is preferable because the reliability of the cutting edge in the bottom finish processing is particularly high when a work material that is likely to be work hardened or a work-affected layer is formed on the surface of the work material by processing under high efficiency conditions.

Specifically, the point where the radial rake angle (true rake angle) of the corner R cutting edge is the minimum value is located in the region where the radial angle of the corner R cutting edge is 5 ° or more, so that the bottom finish processing is performed. It is possible to remarkably increase the machining accuracy by preventing the deterioration of the sharpness of the time, and to extend the tool life.
In addition, the point at which the radial rake angle (true rake angle) of the corner R cutting edge is the minimum value is located in the region of the corner R cutting edge where the radial angle is 50 ° or less. The cutting edge strengthening part formed in the part is likely to be within the range of a general bottom finishing allowance. Therefore, the effect of preventing chipping at the boundary portion of the cutting edge can be remarkably obtained regardless of the finishing cost for bottom finishing.

The present invention improves the cutting performance particularly when machining a long tool protrusion (for example, L / D is 4 or more) when finishing the bottom surface serving as a machining reference surface or a side surface perpendicular to a horizontal surface on a work material such as a mold. In addition to the finishing dimensional accuracy of the bottom surface of the work material, it is possible to provide a blade-tip-exchange-type rotary cutting tool and an insert excellent in dimensional accuracy in side surface finishing processing perpendicular to the horizontal plane.

The perspective view of the blade-tip-exchange-type rotary cutting tool which is an example of embodiment of this invention is shown. The top view of the blade-tip-exchange-type rotary cutting tool shown in FIG. 1 is shown. The side view of the blade-tip-exchange-type rotary cutting tool shown in FIG. 1 is shown. The front view of the blade-tip-exchange-type rotary cutting tool shown in FIG. 1 is shown. The perspective view of the insert with which the blade edge | tip exchange type rotary cutting tool shown in FIG. 1 was mounted | worn is shown. The top view which expanded the corner R cutting blade part vicinity of the insert shown in FIG. 5 is shown. The side view which expanded the corner R cutting-blade part vicinity of the insert shown in FIG. 5 is shown. The front view which expanded the corner R cutting edge part vicinity of the insert shown in FIG. 5 is shown. The enlarged view of the corner R cutting blade part vicinity shown in FIG. 5 is shown. The figure explaining the radial rake angle and radial angle in the corner R cutting edge of the blade-tip-exchange-type rotary cutting tool of this embodiment is shown. The profile of the radial rake angle in the corner R cutting edge of the blade edge | tip-exchange-type rotary cutting tool of this embodiment is shown. The insert shape of the comparative example 2 is shown. The insert shape of the comparative example 3 is shown. The shape profile line of the standing wall side part formed by the process using the insert of this invention example 1 is shown. The shape profile line of the standing wall side part formed by the process using the insert of the comparative example 2 is shown. The shape profile line of the standing wall side part formed by the process using the insert of the comparative example 3 is shown. The shape profile line of the standing wall side part formed by the process using the insert of this invention example 1 is shown. The shape profile line of the standing wall side part formed by the process using the insert of the comparative example 2 is shown. The shape profile line of the standing wall side part formed by the process using the insert of the comparative example 3 is shown.

Hereinafter, an embodiment of a blade edge replaceable radius end mill according to the present invention will be described with reference to the drawings. In the present embodiment, the blade edge exchange type rotary cutting tool of the present invention is applied to a blade edge exchange type radius end mill (hereinafter referred to as “blade edge exchange type radius end mill”). This blade-tip-exchange-type rotary cutting tool is particularly suitable for side finishing of a work material performed under cutting conditions with a long tool protrusion (L / D is 4 or more). Here, the L value indicates the length of the tool in the rotation center axis (C) direction, and the D value indicates the diameter of the rotation locus of the tool cutting edge.
One of the reasons why it is suitable for side finishing with long tool overhang is to provide corner chamfering by providing a chamfered surface (15) with a negative rake angle (Ar1) in the corner R cutting edge (13). This is because the biting of the blade (13) and the outer peripheral cutting edge (9) on the work material has been improved.

The embodiment of the present invention described below includes a rake face (14) of a corner R cutting edge (13) connecting a bottom cutting edge (11) and an outer peripheral cutting edge (9), and a rake face (12) of the bottom cutting edge. It is a blade-tip-exchange-type rotary cutting tool in which an insert (5) having a chamfered surface (15) combined with at least a portion located outside in the radial direction is detachably attached to a tool body (1). The blade end replaceable radius end mill (6) will be described.

FIG. 1 is a perspective view showing an example of the configuration of a blade end replaceable radius end mill (6) which is an example of an embodiment of the present invention.
FIG. 2 is a plan view of the blade end replaceable radius end mill (6) shown in FIG.
FIG. 3 is a side view of the blade end replaceable radius end mill (6) shown in FIG.
FIG. 4 is a front view of the blade end replaceable radius end mill (6) shown in FIG.
FIG. 5 is a perspective view showing the insert (5) of the blade end replaceable radius end mill (6) shown in FIG.

[Schematic configuration of the blade end replaceable radius end mill]
As shown in FIGS. 1 to 4, the blade end replaceable radius end mill (6) includes a tool body (1) having a substantially cylindrical shape, and a tip portion (2) in the direction of the rotation center axis (C) of the tool body (1). And an insert (5) having a cutting edge portion (4).
A shank portion (not shown) is formed integrally with the tool body (1) at the base end in the direction of the rotation center axis (C) of the tool body (1).

The blade end replaceable radius end mill (6) of the present embodiment includes a tool body (1) formed of steel, cemented carbide, or the like, and an insert (5) formed of cemented carbide, etc. A plate-like insert (5) is placed on the mounting seat (insert mounting seat) (3) formed at the tip (2) of the tool body (1) rotated about the rotation center axis (C). The shaft (symmetrical axis of the cutting edge portion (4) formed on the insert (5)) is detachably mounted in a state where the shaft is aligned with the rotation center axis (C) of the tool.
The insert (5) attached to the attachment seat (3) is disposed so that the cutting edge (4) protrudes to the tip side and the radially outer side of the tool body (1).

The blade end replaceable radius end mill (6) has a base end (shank) of the tool body (1) attached to a spindle (not shown) of a machine tool indirectly or directly via a chuck. As the main shaft is driven to rotate, it is rotated in the tool rotation direction (R) around the rotation center axis (C) to subject the workpiece made of a metal material or the like to rolling (milling). .

[Definition of direction (direction) used in this embodiment]
In the present embodiment, the direction in which the rotation center axis (C) of the tool body (1) extends, that is, the direction parallel to the rotation center axis (C) is referred to as the rotation center axis (C) direction. Of the rotation center axis (C) direction, the direction from the shank portion of the tool body (1) to the mounting seat (3) is referred to as the tip side (the lower side in FIGS. 2 and 3), and the mounting seat (3). The direction from the base to the shank is referred to as the base end side (the upper side in FIGS. 2 and 3).

A direction orthogonal to the rotation center axis (C) is referred to as a radial direction. Of the radial directions, a direction approaching the rotation center axis (C) is referred to as an inner side in the radial direction, and a direction away from the rotation center axis (C) is referred to as an outer side in the radial direction.
Further, a direction around the rotation center axis (C) is referred to as a circumferential direction. Of the circumferential directions, the direction in which the tool body (1) is rotated by the rotational drive of the spindle during cutting is called the tool rotation direction (R), and the opposite rotation direction is opposite to the tool rotation direction (R). The side (that is, the counter tool rotation direction).

The definition of the direction (direction) described above is applied to the entire blade end replaceable radius end mill (6), as well as the rotation center axis (C) of the blade end replaceable radius end mill (6). The same applies to the insert (5) in which the insert central axes are aligned (coaxially arranged).

[Mounting seat]
The mounting seat (3) includes a slit-like insert fitting groove (7) formed in the distal end portion (2) of the tool body (1) and extending in the radial direction including the rotation center axis (C) of the tool. A fixing screw (8) for fixing the insert (5) inserted in the insert fitting groove (7).

As shown in FIGS. 3 and 4, the insert mounting seat (3) opens at the tip (2) of the tool main body (1), and further extends in the radial direction of the tool main body (1) to provide the tool main body (1). ) And a slit-like insert fitting groove (7) formed in a predetermined length (depth) toward the base end side of the tool body (1).

By forming the slit-like insert fitting groove (7) in the tip portion (2) of the tool body (1), the tip portion (2) of the tool body (1) is divided into two, and a pair of tips. A half body is formed. An insert fixing screw hole is formed from one surface of the tip half so as to cross the insert fitting groove (7) and reach the other tip half. The direction of the screw hole for fixing the insert is formed in a direction orthogonal to the direction in which the insert fitting groove (7) of the tool body (1) extends in the radial direction of the tool body (1).
In addition, a female screw for fitting with the male screw portion of the fixing screw (8) is inserted into the inner peripheral surface of the screw hole for fixing the insert that passes through the first half portion and reaches the other half portion. Screw part is engraved.

〔insert〕
A configuration example of the insert (5) having a cutting edge will be described with reference to FIGS.
FIG. 5 is a perspective view of the insert (5) of the example of the present invention.
FIG. 6 is an enlarged plan view of the vicinity of the corner R cutting edge (13) of the insert (5) shown in FIG.
FIG. 7 is an enlarged side view of the vicinity of the corner R cutting edge (13) of the insert (5) shown in FIG.
FIG. 8 is an enlarged front view of the vicinity of the corner R cutting edge (13) of the insert (5) shown in FIG.
FIG. 9 is an enlarged view of the vicinity of the corner R cutting edge (13) shown in FIG.
FIG. 10 is a diagram for explaining the radial rake angle (δ) and the radial angle (θ) in the corner R cutting edge (13) of the blade end replaceable radius end mill (6) of the present embodiment.
FIG. 11 is a profile of a radial rake angle in the corner R cutting edge (13) of the blade end replaceable radius end mill (6) of the present embodiment.

As shown in FIG. 5, the insert (5) has a substantially flat plate shape and has a thickness T as shown in FIG. The insert (5) is provided with a screw insertion hole (18) into which a fixing screw (8) for fixing the insert (5) to the mounting seat (3) is inserted, and for cutting and cutting the work material. A cutting edge portion (4).

As shown in FIG. 5, the insert (5) includes a screw insertion hole (18) penetrating from one outer surface portion (5a) toward the other outer surface portion (5b). The screw insertion hole (18) is a through hole through which the fixing screw (8) is inserted when the insert (5) is mounted and fixed to the mounting seat (3).

The cutting edge portion (4) is formed on a rake face that faces the tool rotation direction (R), a flank face that intersects the rake face and faces the radially outer side or the tip side, and an intersecting ridge line of the rake face and the flank face. And a cutting edge. The cutting edge includes an outer peripheral cutting edge (9), a bottom cutting edge (11), and a corner R cutting edge (13). The cutting edge includes a peripheral cutting edge (9), a bottom cutting edge (11), and a corner R cutting edge (13), and thus has a substantially L shape as a whole. Further, a rake face and a flank face are arranged adjacent to each of the cutting edges (9, 11, 13).

The insert (5) of the present embodiment is a two-blade cutting insert, and has two sets of the above-mentioned cutting blades provided with an outer peripheral cutting blade (9), a bottom cutting blade (11), and a corner R cutting blade (13). The two sets of cutting edges are arranged 180 degrees rotationally symmetrical about the rotation center axis (C).

Reference numeral “9” shown in FIGS. 5 and 6 is the outer peripheral cutting edge (9) of the insert (5). The outer peripheral cutting edge (9) extends along the direction of the rotation center axis (C). Specifically, the outer peripheral cutting edge (9) is twisted in a spiral shape toward the side opposite to the tool rotation direction (R) as it goes from the tip end connected to the corner R cutting edge (13) toward the base end side. It extends. That is, as shown in FIG. 3, the torsion angle (ε) of the outer peripheral cutting edge (9) is a positive value (positive angle). The magnitude of the twist angle (ε) of the outer peripheral cutting edge (9) is not particularly limited, but is preferably in the range of 2 ° to 20 °. Thereby, the effect which reduces cutting resistance and the effect which improves chip discharge | emission property are acquired with sufficient balance. Further, the range of the magnitude of the twist angle (ε) of the outer peripheral cutting edge (9) is more preferably 2 ° to 15 °, and particularly preferably 3 ° to 8 °.
When the insert (5) is mounted on the mounting seat (3) and the blade end replaceable radius end mill (6) is rotated about the rotation center axis (C), the rotation locus of the pair of outer peripheral cutting edges (9) is cylindrical. Formed.

When the insert (5) is mounted in the mounting seat (3) (insert fitting groove 7) of the tool body (1), as shown in FIGS. 6 and 9, the outer peripheral cutting edge (9) and the corner R cutting edge The boundary point (Q) with (13) is the outermost peripheral point in the direction perpendicular to the rotation center axis (C) (that is, the radial direction). At the boundary point (Q), the distal end of the outer peripheral cutting edge (9) and the base end of the corner R cutting edge (13) are connected. That is, the cutting edge from the boundary point (Q) toward the proximal end is the outer peripheral cutting edge (9), and the cutting edge from the boundary point (Q) toward the distal end is the corner R cutting edge (13).

The rake face (10) of the outer peripheral cutting edge (9) facing the tool rotation direction (R) is disposed adjacent to the radially inner side of the outer peripheral cutting edge (9). A chip discharge groove (17) is formed on the radially inner side of the rake face (10) of the outer peripheral cutting edge (9). The chip discharge groove (17) extends along the rotation center axis (C) direction.

The flank of the outer peripheral cutting edge (9) is disposed adjacent to the opposite side of the outer peripheral cutting edge (9) from the tool rotation direction (R). The flank face is formed facing outward in the radial direction, and is inclined so as to go radially inward from the outer peripheral cutting edge (9) toward the side opposite to the tool rotation direction (R). Is granted.

Reference numeral “11” shown in FIGS. 5 and 6 is the bottom cutting edge (11) of the insert (5). The bottom cutting edge (11) extends along the radial direction. Specifically, the bottom cutting edge (11) extends toward the base end side from the radial outer end adjacent to (connected to) the corner R cutting edge (13) toward the inner side in the radial direction, and has a center of rotation. It is slightly inclined with respect to a plane (horizontal plane) perpendicular to the axis (C).
When the insert (5) is mounted on the mounting seat (3) and the blade end replaceable radius end mill (6) is rotated about the rotation center axis (C), the rotation locus of the pair of bottom cutting edges (11) is substantially conical. It is formed in a shape.

When the insert (5) is mounted in the mounting seat (3) (insert fitting groove 7) of the tool body (1), as shown in FIGS. 6 and 9, the corner R cutting edge (13) and the bottom cutting edge The boundary point (P) with (11) is located at the foremost part of the tool in the direction of the rotation center axis (C), that is, the lowest point. At the boundary point (P), the radially outer end of the bottom cutting edge (11) and the radially inner end of the corner R cutting edge (13) are connected. That is, the cutting edge that extends radially inward from the boundary point (P) is the bottom cutting edge (11), and the cutting edge that extends radially outward from the boundary point (P) is the corner R cutting edge (13). In addition, the code | symbol "U" of FIG. 6 shows the bottom cutting edge area | region which is a cutting edge line | wire area | region which went to the bottom cutting edge (11) side (diameter inside) from the position of the boundary point (P).

The rake face (12) of the bottom cutting edge (11) facing the tool rotation direction (R) is disposed adjacent to the base end side of the bottom cutting edge (11). A chip discharge groove (16) is formed on the base end side of the rake face (12) of the bottom cutting edge (11). The chip discharge groove (16) extends along the direction of the rotation center axis (C). The chip discharge groove (16) of the bottom cutting edge (11) is disposed adjacent to the inner side in the radial direction of the chip discharge groove (17) of the outer peripheral cutting edge (9), and these chip discharge grooves (16, 17) are arranged with each other. Are formed by different surfaces.

The flank of the bottom cutting edge (11) is disposed adjacent to the side of the bottom cutting edge (11) opposite to the tool rotation direction (R). The flank is formed so as to face the distal end side, and is inclined so as to go to the base end side from the bottom cutting edge (11) toward the side opposite to the tool rotation direction (R). Has been granted.

In the example shown in the present embodiment, the bottom cutting edge (11) is located on the outer side in the radial direction in the blade length region (full length) of the bottom cutting edge (11), and the corner R cutting edge (13). And an outer bottom cutting edge (19) extending radially inward from the corner R cutting edge (13), and of the blade length region, the outer bottom cutting edge (19) is more radial than the outer bottom cutting edge (19). An inner bottom cutting edge (20) which is disposed on the inner side and extends radially inward from the outer bottom cutting edge (19). And the part corresponding to an outer side bottom cutting edge (19) among bottom cutting edges (11) is arrange | positioned in the said bottom cutting edge area | region (U).

In the plan view of the insert (5) shown in FIG. 6, that is, the plan view in which the rake face (12) of the bottom cutting edge (11) is viewed in front, the outer bottom cutting edge (19) of the bottom cutting edge (11) and The inner bottom cutting edge (20) extends in a straight line so as to form one straight line having no bending point at the connecting portion.
However, the amount of displacement of the rake face (12) of the bottom cutting edge (11) in the circumferential direction per unit length in the direction of the rotation center axis (C), that is, the rotation center axis (C) of the rake face (12). The inclination with respect to the direction is larger at the outer bottom cutting edge (19) than at the inner bottom cutting edge (20).

Specifically, the axial rake angle (axial rake) of the bottom cutting edge (11) is larger on the negative angle (negative angle) side at the outer bottom cutting edge (19) than at the inner bottom cutting edge (20). Yes. That is, the absolute value of the axial rake angle of the outer bottom cutting edge (19) is larger than that of the inner bottom cutting edge (20).
This is because the portion corresponding to the outer bottom cutting edge (19) of the rake face (12) of the bottom cutting edge (11) is disposed on the chamfered surface (15). The chamfered surface (15) will be described later separately. In the example of this embodiment, the axial rake angle of the inner bottom cutting edge (20) is 0 °, and the axial rake angle of the outer bottom cutting edge (19) is a negative value.

In the front view of the insert (5) shown in FIG. 8, that is, the front view of the insert (5) viewed from the distal end of the rotation center axis (C) toward the proximal end side, in the radial direction of the bottom cutting edge (11) The amount of displacement in the circumferential direction per unit length, that is, the inclination of the bottom cutting edge (11) with respect to the radial direction is larger at the outer bottom cutting edge (19) than at the inner bottom cutting edge (20). Specifically, the central rake angle (radial rake; radial rake angle) of the bottom cutting edge (11) is a negative angle (negative angle) at the outer bottom cutting edge (19) than the inner bottom cutting edge (20). The side is getting bigger. That is, the absolute value of the rake angle in the center direction of the outer bottom cutting edge (19) is larger than that of the inner bottom cutting edge (20). In the example of the present embodiment, the rake angle in the center direction of the inner bottom cutting edge (20) and the rake angle in the center direction of the outer bottom cutting edge (19) are both negative values.

The code | symbol "13" shown in FIG. 5 is the corner R cutting edge (13) which connects the bottom cutting edge (11) and outer periphery cutting edge (9) of insert (5). The corner R cutting edge (13) connects the outer end in the radial direction of the bottom cutting edge (11) and the tip of the outer peripheral cutting edge (9) and is directed toward the outer periphery of the tip of the tool body (1). It is formed in a convex arc shape.
When the insert (5) is mounted on the mounting seat (3) and the blade end replaceable radius end mill (6) is rotated about the rotation center axis (C), the rotation locus (rotation locus) of the pair of corner R cutting edges (13) The shape of the cross section including the rotation center axis (C) and parallel to the direction of the rotation center axis (C) is formed in a substantially ¼ arc shape.

When the insert (5) is mounted on the mounting seat (3) (insert fitting groove 7) of the tool body (1), the corner R cutting edge (13) is cut off at the bottom as shown in FIGS. An arcuate blade connecting from the lowest point (boundary point P) of the tool positioned at the radially outer end of the blade (11) to the outermost peripheral point (boundary point Q) of the tool positioned at the tip of the outer peripheral cutting edge (9); Become.

The rake face (14) of the corner R cutting edge (13) facing the tool rotation direction (R) is disposed adjacent to the radially inner side and the base end side of the corner R cutting edge (13). The rake face (14) of the corner R cutting edge (13) is gradually inclined toward the tool rotation direction (R) toward the base end side in the rotation center axis (C) direction. That is, the rake angle (Ar) in the axial direction of the corner R cutting edge (13) is set to a negative angle (negative angle) throughout the corner R cutting edge (13). For this reason, as shown in FIG. 9, the axial rake angle (Ar1) of the corner R cutting edge (13) at the boundary point (Q) between the corner R cutting edge (13) and the outer peripheral cutting edge (9) is negative. The axial rake angle (Ar2) of the corner R cutting edge (13) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) also has a negative value. .

9 represents the radial rake angle (radial rake angle) of the corner R cutting edge (13), and in FIG. 9, the diameter of the corner R cutting edge (13) at the boundary point (Q). Directional rake angles are shown. In the corner R cutting edge (13), the radial rake angle (Rr) is set to a negative angle (negative angle) between the boundary point (Q) and the boundary point (P) along the blade length region. Preferably it is.

The flank face of the corner R cutting edge (13) is arranged adjacent to the opposite side of the corner R cutting edge (13) from the tool rotation direction (R). The flank has a curved surface that is convex toward the outer periphery of the tip of the tool body (1), and is formed radially outward and toward the tip. The flank is inclined so as to be directed radially inward and proximally from the corner R cutting edge (13) toward the side opposite to the tool rotation direction (R), thereby providing a clearance angle.

6 is a chamfered surface (15) in which the rake face (14) of the corner R cutting edge (13) and the rake face (12) of the bottom cutting edge (11) are combined. The chamfered surface (15) is a portion positioned at least on the radially outer side of the rake face (14) of the corner R cutting edge (13) and the rake face (12) of the bottom cutting edge (11) (this embodiment). In this example, the outer bottom cutting edge (19) is included. In other words, the chamfered surface (15) of the present embodiment serves as the rake face (14) of the entire corner R cutting edge (13) and the rake face of the outer bottom cutting edge (19) of the bottom cutting edge (11). ing.

As shown in FIGS. 6 and 9, the chamfered surface (15) is a boundary point existing in the outer bottom cutting edge (19), the corner R cutting edge (13), and the region (S) of the bottom cutting edge (11). It is formed in a region surrounded by a curved ridge line connecting (Q) and the point G on the rake face and a straight ridge line connecting the point G and the point F on the bottom cutting edge (11). In addition, the said area | region (S) is an area | region ranging from the front-end | tip part of the formation scheduled area | region of an outer periphery cutting edge (9) to the base end part of the formation scheduled area | region of a corner R cutting edge (13). The relationship between the region (S) and the boundary point (Q) will be described separately in an embodiment described later. The point G is an intersection where a total of three surfaces of the pair of chip discharge grooves (16, 17) and the chamfered surface (15) intersect. From this point G, a ridge line (chip discharge groove ( 16 and 17) and a ridge line that forms a boundary between the chamfered surfaces (15)) extend radially. The point F is a connection point between the outer bottom cutting edge (19) and the inner bottom cutting edge (20) of the bottom cutting edge (11).
In the example of this embodiment, the chamfered surface (15) is a planar region formed by being surrounded by the above-mentioned cutting edge and ridgeline.

[Radial Rake Angle and Radiation Angle of Corner R Cutting Edge]
The blade end replaceable radius end mill (6) has the following special technical features in the vicinity of the corner R cutting edge (13) of the cutting edge portion (4).
Reference sign “Pr” shown in FIG. 10 is a reference plane perpendicular to the main motion direction (tool rotation direction R) of the tool of the blade end replaceable radius end mill (6). The reference plane (Pr) is a virtual plane including the rotation center axis (C). In the present embodiment, as shown in FIG. 10, a predetermined point (A) on the corner R cutting edge (13) is the plane. Contained within. Moreover, the upper left figure of FIG. 10 is an enlarged view of the vicinity of the corner R cutting edge portion of the insert as seen from the direction perpendicular to the reference plane (Pr).

The symbol “O” is the arc center point of the corner R cutting edge (13).
The symbol “VL” is an imaginary straight line passing through the arc center point (O) of the corner R cutting edge (13) and the predetermined point (A) of the corner R cutting edge (13).
The cross section (hatched surface) of the insert (5) indicated by reference sign “VS” in the lower right diagram of FIG. 10 is a virtual plane that is perpendicular to the reference surface (Pr) and includes a virtual straight line (VL). .

What is indicated by a symbol “δ” is an angle at which the rake face (14) of the corner R cutting edge (13) is inclined with respect to the reference plane (Pr) in the virtual plane (VS) (virtual straight line (VL and rake face). (An angle formed with (14))). The radial rake angle (δ) is the true rake angle. In this embodiment, the radial rake angle (δ) is changed by moving a predetermined point (A) on the corner R cutting edge (13) on the corner R cutting edge (13). In other words, the radial rake angle (δ) varies depending on the position of the point (A) on the corner R cutting edge (13).
What is indicated by the symbol “η” is a clearance angle at a predetermined point (A) of the corner R cutting edge (13). In other words, a straight line perpendicular to the virtual straight line (VL) and the corner R on the virtual plane (VS). It is an angle formed by the flank of the cutting edge (13).

What is indicated by a symbol “θ” is a radiation angle that is an angle at which the virtual straight line (VL) is inclined with respect to the rotation center axis (C). Specifically, the radiation angle (θ) is determined by the virtual straight line (VL) projected on the reference plane (Pr) (that is, the virtual straight line (VL) in FIG. 10) within the reference plane (Pr). It is an angle inclined with respect to C). The “virtual straight line (VL) projected on the reference plane (Pr)” refers to projecting the virtual straight line (VL) perpendicular to the reference plane (Pr).

Then, as shown in FIG. 11 showing the relationship between the radial angle (θ) of the corner R cutting edge (13) and the radial rake angle (δ), the radial rake angle (δ) of the corner R cutting edge (13) is In the entire length of the corner R cutting edge (13), it has a negative value and continuously changes.
Further, the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (P) (that is, θ = 0 °) between the corner R cutting edge (13) and the bottom cutting edge (11) is the corner R It is smaller than the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (Q) (that is, θ = 90 °) between the cutting edge (13) and the outer peripheral cutting edge (9).
In FIG. 11, the data at the right end at θ = 90 ° is the true rake angle of the outer peripheral cutting edge (9) at the boundary point (Q) between the corner R cutting edge (13) and the outer peripheral cutting edge (9). Yes, with a positive value.

In this embodiment, the value of the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (P) (radiation angle θ = 0 °) is the boundary point (Q) (radiation angle θ = 90 °). ) In the radial direction rake angle (δ) of the corner R cutting edge (13) in FIG. 11 is increased twice or more to the negative angle side (negative angle side). In the example shown in FIG. That's it.

In addition, as shown in FIG. 11, the radial rake angle (δ) is the minimum value in the intermediate portion located between the pair of boundary points (P, Q) in the corner R cutting edge (13). Become. In other words, the radial rake angle (δ) is largest on the negative angle side in the intermediate portion located between the pair of boundary points (P, Q). In addition, the intermediate part located between a pair of boundary points (P, Q) is a region (0 ° <θ <90 °) excluding the boundary point (P, Q) in the corner R cutting edge (13). It is.
Specifically, the minimum value of the radial rake angle (δ) is set in the range of 5 ° to 50 ° in the radial angle (θ) of the corner R cutting edge (13). In other words, the point at which the radial rake angle (δ) has the minimum value is located in the corner R cutting edge (13) where the radial angle (θ) is 5 ° or more and 50 ° or less. In the example shown in FIG. 11, the radial rake angle (δ) has a minimum value in the range of 10 ° to 30 ° (particularly around 20 °) in the radiation angle (θ).

[Effects of this embodiment]
The blade tip replaceable radius end mill (6) and the insert (5) of the present embodiment described above have the boundary point (Q) (the outermost peripheral position) between the arcuate corner R cutting edge (13) and the outer peripheral cutting edge (9). ) Has a negative value in the axial rake angle (Ar1) of the corner R cutting edge (13), and the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) (the most advanced position) ), The axial rake angle (Ar2) of the corner R cutting edge (13) has a negative value. That is, the axial rake angle (Ar) of the corner R cutting edge (13) is a negative angle. The twist angle (ε) of the outer peripheral cutting edge (9) has a positive value and is a positive angle.

Since the blade end replaceable radius end mill (6) and the insert (5) of this embodiment have this configuration, the boundary point (Q) between the corner R cutting edge (13) and the outer peripheral cutting edge (9) Among the circumferential directions around the rotation center axis (C), this is the point that protrudes most toward the tool rotation direction (R) (the most convex point). For this reason, in the side finishing process for machining a wall surface (vertical surface, standing wall) perpendicular to the horizontal plane with respect to the work material, the corner R cutting edge (13) and the outer peripheral cutting edge (9) are arranged at the boundary point (Q ) Cutting of the work material is started by point contact with the work material at the most convex point. Therefore, the biting of the cutting edge on the work material is improved.

Cutting started by point contact from the boundary point (Q) expands the cutting range to the corner R cutting edge (13) and the outer peripheral cutting edge (9) as the tool rotates. Since the axial rake angle (Ar1) of the corner R cutting edge (13) is set to a negative angle, the corner R cutting edge (13) has a reverse twisted blade shape. The outer peripheral cutting edge (9) has a positive twisted blade shape. For this reason, out of the cutting resistance received by the tool from the work material, the cutting resistance (that is, the back force) acting in the direction along the rotation center axis (C) is the rotation center axis (C ) Direction toward the distal end side (blade edge side), while the corner R cutting edge (13) acts toward the base end side (tool shank side) in the direction of the rotation center axis (C).
Thereby, the cutting resistance which acts toward the blade edge side in the outer peripheral cutting edge (9) can be canceled. Therefore, it is possible to improve the phenomenon that the tool body (1) is bent by the cutting resistance applied to the cutting edge side in the direction of the rotation center axis (C).

In addition, it is possible to suppress the escape amount of the outer peripheral cutting edge (9) from the work material, which affects the dimensional accuracy in the side surface finishing process perpendicular to the horizontal surface of the work material, and to set the work reference surface serving as the vertical side surface in the vertical direction. Finishing can be done with extremely high precision from the upper part to the lower part. In addition, since the biting of the outer peripheral cutting edge (9) and the corner R cutting edge (13) on the work material is started by point contact, the occurrence of chatter vibration is reduced and the effect of stabilizing the processing is obtained. It is done.

The radial rake angle (δ) has a negative value over the entire length of the corner R cutting edge (13). Further, the radial rake angle (δ) has a minimum value in an intermediate portion of the corner R cutting edge (13) located between the pair of boundary points (P, Q).
Thus, since the radial rake angle (δ) of the corner R cutting edge (13) at the pair of boundary points (P, Q) is both negative (negative angle), the corner R The cutting edge strength of the cutting edge (13) can be sufficiently ensured.
On the other hand, unlike the present embodiment, for example, one or both of the radial rake angles (δ) of the corner R cutting edge (13) at the pair of boundary points (P, Q) are positive values ( In the case of a positive angle), the strength of the corner R cutting edge (13) is lowered, which is inconvenient.

In addition, since the radial rake angle (δ) has a minimum value at an intermediate portion between the pair of boundary points (P, Q) of the corner R cutting edge (13), these boundary points (P, Q ), The radial rake angle (δ) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) is set to a negative value while being a negative value ( It can be close to the positive angle side). Thereby, the sharpness of the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) can be ensured in the bottom finishing.

Further, from the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11), the corner R cutting edge (13) and the outer peripheral cutting edge (9) along the corner R cutting edge (13). The rake angle (δ) in the radial direction becomes smaller as it goes toward the boundary point (Q) (specifically, as it goes toward the intermediate portion). That is, the radial rake angle (δ) increases toward the negative angle side (negative angle side) as it approaches the intermediate portion, and reaches a minimum value (that is, maximum value on the negative angle side) on the intermediate portion. Therefore, the edge strength can be remarkably improved by providing the intermediate portion located between the pair of boundary points (P, Q) at the cutting edge boundary portion for cutting the work hardened layer of the work material. . Therefore, it is preferable because the reliability of the cutting edge in the bottom finish processing is particularly high when a work material that is likely to be work hardened or a work-affected layer is formed on the surface of the work material by processing under high efficiency conditions.

As described above, according to the present embodiment, when finishing a bottom surface serving as a processing reference surface or a side surface perpendicular to a horizontal surface on a work material such as a die, machining with a particularly long tool protrusion (for example, L / D is 4 or more). In addition to the finishing dimensional accuracy of the bottom surface of the work material, the dimensional accuracy in the side surface finishing processing perpendicular to the horizontal plane can be remarkably improved.

In the present embodiment, the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) is the corner R cutting edge ( 13) and the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (Q) between the outer peripheral cutting edge (9).
That is, the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) is the corner R cutting edge (13) and the outer periphery. Since it is larger on the negative angle side (negative angle side) than the radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (Q) with the cutting edge (9), the bottom cutting edge ( 11) Improvement of chipping resistance and improvement of chip discharge can be achieved, and the finished surface can be maintained in high quality.

Further, the rake angle (δ) in the radial direction of the corner R cutting edge (13) at the boundary point (Q) between the corner R cutting edge (13) and the outer peripheral cutting edge (9) is a positive value while setting a negative value. The tool can be moved closer to the side (positive angle side), so in the side finishing process for machining the wall surface (vertical wall) perpendicular to the work material, the tool radial direction (horizontal direction) that the tool cut into the work material receives from the work material It is possible to reduce the cutting resistance (i.e., the feed component force) to the surface. Thereby, chatter vibration is suppressed and the machined surface accuracy can be improved.

More specifically, for example, the radial rake angle (δ) (true rake angle) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) is α, and the corner R cutting edge (13 ) And the radial rake angle (δ) (true rake angle) at the boundary point (Q) between the outer peripheral cutting edge (9) and the radial rake angle (δ) (true rake angle) in the intermediate portion. When the minimum value is γ, the radial rake angle α, the radial rake angle β, and the radial rake angle γ all have negative values, and the radial rake angle α value, β value, and γ value. Where | α |, | β |, and | γ | are the absolute values of | γ |> | α |> | β |.

By having this configuration, the blade end replaceable radius end mill (6) is a cut that hits the work hardening layer of the work material in advance roughing or intermediate finishing in bottom finishing and side finishing (especially bottom finishing). The radial rake angle (δ) of the blade boundary portion (intermediate portion located between the pair of boundary points P and Q) can be set to the smallest negative value.
This is preferable because the effect of preventing chipping at the boundary of the cutting edge can be remarkably obtained in roughing or intermediate finishing.
On the other hand, unlike the present embodiment, when the above-mentioned | γ |> | α |> | β | is not satisfied, the cutting edge is used in bottom finishing or side finishing (particularly bottom finishing). The boundary may be easily damaged.

In this embodiment, the angle at which the virtual straight line (VL) projected onto the reference plane (Pr) is inclined with respect to the rotation center axis (C) in the reference plane (Pr) is defined as the radiation angle (θ). Then, the point where the radial rake angle (δ) becomes the minimum value is located in the corner R cutting edge (13) in the region where the radial angle (θ) is 5 ° or more and 50 ° or less. The following effects are exhibited.

While the blade end replaceable radius end mill (6) has this configuration, while ensuring the sharpness of the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) in the bottom finishing process, The edge strength of the cutting edge boundary portion (intermediate portion located between the pair of boundary points P and Q) for cutting the work hardened layer of the work material can be improved. Therefore, it is preferable because the reliability of the cutting edge in the bottom finish processing is particularly high when a work material that is likely to be work hardened or a work-affected layer is formed on the surface of the work material by processing under high efficiency conditions.

Specifically, the point at which the radial rake angle (δ) (true rake angle) of the corner R cutting edge (13) is the minimum value is that the radial angle (θ) on the corner R cutting edge (13) is 5 ° or more. By being located in the region, it is possible to prevent the sharpness from being lowered during the bottom finishing process, to remarkably increase the machining accuracy, and to extend the tool life.
Moreover, the point which becomes the minimum value of the radial rake angle (δ) (true rake angle) of the corner R cutting edge (13) is that the radial angle (θ) on the corner R cutting edge (13) is 50 ° or less. By being located in this area, the cutting edge reinforcing portion formed in this minimum value portion is likely to be within the range of a general bottom finishing allowance. Therefore, the effect of preventing chipping at the boundary portion of the cutting edge can be remarkably obtained regardless of the finishing cost for bottom finishing.

[Other configurations included in the present invention]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, the minimum value of the radial rake angle (δ) is set in the range of 5 ° or more and 50 ° or less in the radiation angle (θ) of the corner R cutting edge (13). However, the present invention is not limited to this. That is, the minimum value of the radial rake angle (δ) may be set to be less than 5 ° or more than 50 ° in the radiation angle (θ).

In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modification, and a remark etc., addition of a structure, omission, substitution, others It can be changed. The present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to this embodiment.

[Production and cutting test of radius end mill with replaceable cutting edge]
First, as the present invention example 1 which is an example of the present invention, a blade end replaceable radius end mill (6) of the above-described embodiment was prepared.
As the tool body (1), a carbide shank type having a cutting edge diameter (blade diameter) of 20 mm, a shank diameter of 20 mm, a total length of 220 mm, a neck length of 120 mm, and a neck diameter of 19 mm was used.

As the base material of the tool body (1), a base material obtained by joining a cemented carbide and a SKD61 equivalent material with a brazing material was used, and after adjusting the external shape by lathe processing, the shank portion was finished by polishing.
Moreover, the insert fixing | fixed part (insert fitting groove | channel 7) of the attachment seat (3) was formed by milling in the machining center. The fixing screw (8) for attaching and detaching the insert (5) was a screw size having a nominal diameter of M6 and a pitch of 0.75 mm.

The base material of the insert (5) was made of a WC—Co type cemented carbide, and the coating film on the surface of the insert was provided with a CrSi type nitride film.
The shape of the insert (5) is substantially flat as shown in FIG. 5, the R dimension of the corner R cutting edge (13) is 1 mm, and the thickness dimension T value shown in FIG. 8 is 5.2 mm, as shown in FIG. The length of the outer peripheral cutting edge (9) in the side view of the insert was 7 mm, and the axial rake angle (that is, the twist angle ε) of the outer peripheral cutting edge (9) in the side view of the insert was 4 ° as a positive value. The rake angle in the radial direction of the outer peripheral cutting edge (9) (rake angle when viewed from the direction orthogonal to the rotation center axis (C)) was set to 0.5 °.
The bottom cutting edge (11) passes through a boundary point (P) between the bottom cutting edge (11) and the corner R cutting edge (13), and the boundary point (P ) Toward the inner side in the radial direction so as to gradually extend toward the base end in the direction of the central axis of rotation (C), and a positive medium / low gradient angle, which is the inclination angle, was set to 3 °.

The insert shape of Example 1 of the present invention is shown in FIG. The main parameters indicating the shape of the insert (5) of Example 1 of the present invention are shown in Table 1.
The insert (5) of Example 1 of the present invention includes a chamfered surface (15), and the axial rake angle (Ar1) at the position of the boundary point (Q) of the corner R cutting edge (13) and the position of the boundary point (P). The rake angle (Ar2) in the axial direction of the corner R cutting edge (13) was set to −6.8 ° which is the same negative value.

Here, as described above, the boundary point (Q) shown in FIG. 9 is a boundary point between the corner R cutting edge (13) and the outer peripheral cutting edge (9), and the cutting edge around the rotation center axis (C). In the rotation locus, it is also the outermost peripheral point of the outer peripheral cutting edge (9). Such a theoretical (ideal) boundary point (Q) is a point at which the radiation angle (θ) = 90 ° in the corner R cutting edge (13).
However, when the insert (5) is manufactured, if the chamfered surface (15) is actually ground, a region where the outer peripheral cutting edge (9) is to be formed (theoretically, the outer peripheral cutting edge (9) is formed. From the tip of the region where the corner R cutting edge (13) is to be formed to the base end of the region where the corner R cutting edge (13) is to be formed (theoretically, the region where the corner R cutting edge 13 is expected to be formed). A point E to be an actual boundary point (Q) is formed in any part of the region (S). That is, the position of the point E, which is the actual boundary point (Q), may be slightly shifted from the theoretical boundary point (Q) due to various manufacturing circumstances.

In such a case, the corner R cutting edge (13) is located rather than the position of the point E on the region where the outer peripheral cutting edge (9) is to be formed with respect to the theoretical boundary point (Q). It is preferable to be arranged on the side of the formation scheduled region. Thereby, the inconvenience that a tool diameter becomes small can be prevented reliably. In this case, the angle (center angle) between the theoretical boundary point (Q) and the point E (actual boundary point Q) centered on the arc center point (O) is within 2 °. It is preferable.

In view of the above, in Example 1 of the present invention, the point E that is the actual boundary point (Q) is directed from the theoretical boundary point (Q) to the region where the corner R cutting edge (13) is to be formed. Further, the insert (5) was manufactured so as to be disposed within a range of 2 ° or less at the central angle.

Further, in FIG. 6, the point F existing in the bottom cutting edge region (U) was set at a position of 2.5 mm from the straight line passing through the boundary point (Q) and parallel to the rotation center axis (C).

FIG. 11 shows a profile of the radial rake angle (δ) in the corner R cutting edge (13) of Example 1 of the present invention. As shown in FIG. 11, the radial rake angle (δ) had a minimum value at a position where the radiation angle (θ) was 20 °. The radial rake angle (δ) at this time was −7.2 °.
Moreover, the schematic diagram of the cutting edge cross section in the radiation angle ((theta)) 40 degrees of the corner R cutting edge (13) of the example 1 of this invention is shown in FIG. 10 (lower right figure of FIG. 10). An example of the radial rake angle (δ) at a radiation angle (θ) of 40 ° is −6.6 °.
In Table 1, the radial rake angle (δ) when the radiation angle (θ) is 0 ° (boundary point P) is defined as α value, and when the radiation angle (θ) is 90 ° (boundary point Q The rake angle (δ) in the radial direction is indicated as β value, and the minimum value of the rake angle (δ) in the radial direction is indicated as γ value.

Also, a comparative example insert having a technical idea different from that of the present invention was prepared. The insert shape of Comparative Example 2 is shown in FIG. 12, and the insert shape of Comparative Example 3 is shown in FIG. Table 1 also shows the main parameters indicating the shapes of the inserts of Comparative Examples 2 and 3. The insert of the comparative example was manufactured with the same material as the insert of Example 1 of the present invention. However, since the comparative example does not have the special configuration of the present invention, and specifically does not have the chamfered surface of the corner R cutting edge, the specifications of the corner R cutting edge are different from those of the present invention. .

In Comparative Example 3, the rake face of the bottom cutting edge, the rake face of the corner R cutting edge, and the rake face of the outer peripheral cutting edge were formed in the same plane, and the axial rake angle was set to 0 °. Further, the rake face of the bottom cutting edge and the rake face of the corner R cutting edge were formed in the same plane as the chip discharge groove extending to the base end side of the rake face of the bottom cutting edge. The true rake angle of the outer peripheral cutting edge was set to a negative value.

The inserts of Invention Example 1, Comparative Example 2, and Comparative Example 3 produced in this way were mounted on the tool body of a blade end replaceable radius end mill, and cutting evaluation was performed. The tool body with each insert attached was attached to a chuck, which is a tool holder, and then attached to the spindle of the milling machine. Contour line finishing of the standing wall side surface was performed using the following cutting conditions with different cutting speeds (Vc). The falling accuracy of the side surface portion of the workpiece standing wall formed at that time was measured using a shape measuring machine. Table 1 shows the measurement results of the side part tilt accuracy.
The tilt accuracy mentioned here is the tilt accuracy when the shape profile line and vertical line of the work material standing wall side are compared with the apex of the work material standing wall side as a reference. (Μm). That is, when the shape profile line and the vertical line coincide with each other, it indicates that ideal machining can be performed. 14 to 19 show the shape profile lines of the standing wall side surface for each cutting speed (Vc).

In the experiment, an S55C material having a size of 60 × 60 × 30 (mm) was used as the material of the work material. This side shoulder processing was performed, and the standing wall side portion was formed at a depth of 20 mm from the upper surface portion. The measurement location of the tilt accuracy was 10 mm from the top surface at the center and 18 mm from the bottom.

<Cutting conditions>
Work material: Carbon steel S55C (for plastic molds)
Work material hardness: 220HB (Brinell hardness)
Cutting speed (Vc): 100 m / min, 200 m / min Spindle speed (n): 1592 rev / min, 3184 rev / min Feed per tooth (fz): 0.15 mm (constant)
Table feed (Vf): 478 mm / min, 955 mm / min. Axial cut amount (ap): 1 mm (constant)
Radial cut width (ae): 0.1 mm (constant)
Tool overhang: 140 mm
Processing method: Dry type, contour line finishing of the side wall of the standing wall

Table 1 shows the results of measuring and evaluating the falling accuracy of the side wall portion of the work material in the machining with each insert of Invention Example 1, Comparative Example 2, and Comparative Example 3.
When the condition of the cutting speed (Vc value) was 100 m / min, Invention Example 1 provided with a chamfered surface showed a good result with a tilt accuracy of 5 (μm). Furthermore, even when the cutting speed (Vc value) condition, which is a high-efficiency condition, is 200 m / min, it was confirmed that Example 1 of the present invention had a collapse accuracy of 5 (μm) and showed a good result.

In the present invention example 1, the axial rake angle (Ar1) value of the corner R cutting edge (13) at the position of the boundary point (Q) has a negative angle, and the axial rake angle (9) of the outer peripheral cutting edge (9) ( Since the twist angle ε) is set to be a positive angle, the biting of the outer peripheral cutting edge (9) and the corner R cutting edge (13) to the work material is started by point contact, and chattering occurs. It is thought that the generation of vibration is reduced and the machining is stable.

On the other hand, in the comparative example, when the condition of the cutting speed (Vc value) is 100 m / min, the comparative example 2 shows the result of the tilt accuracy of 5 to 12.5 (μm), and in the comparative example 3, Results of 10-15 (μm) were shown. Further, when the condition of the cutting speed (Vc value), which is a high efficiency condition, is 200 m / min, Comparative Example 2 shows a result of the tilt accuracy of 7.5 to 12.5 (μm), and Comparative Example 3 is The results of 17.5 to 27.5 (μm) were shown. From these, the comparative example has confirmed that the fall accuracy is extremely deteriorated by setting the cutting conditions to the high efficiency conditions.
The reason for this is that, since the axial rake angle of the corner R cutting edge that bites into the work material is the same as the axial rake angle (twist angle) of the outer peripheral cutting edge, the biting is started by line contact. In addition, it is considered that the high occurrence rate of chatter vibration has an effect.

In addition, FIGS. 14 to 19 show the shape profile lines of the standing wall side surfaces formed by processing using the inserts of Example 1, Comparative Example 2, and Comparative Example 3 of the present invention. 14 to 16 are shape profile lines when the cutting speed (Vc value) is 100 m / min, and FIGS. 17 to 19 are shape profile lines when the cutting speed (Vc value) is 200 m / min. In these drawings, dotted lines are a horizontal line and a vertical line indicating a bottom surface to be machined and a surface perpendicular to a horizontal plane, and a solid line is a shape profile line.
It can be confirmed that the vertical wall side portion formed by processing using the inserts of Comparative Examples 2 and 3 has a greater deviation from the vertical line as it approaches the bottom, and this tendency is more prominent as the cutting speed increases. It was. On the other hand, the vertical wall side surface formed by processing using the insert of Example 1 of the present invention has a constant deviation from the vertical line from the top to the bottom, and forms a surface perpendicular to the horizontal plane. It has been confirmed that.

The base material of the insert (5) according to Example 1 of the present invention is, for example, cermet, high speed steel, titanium carbide, silicon carbide, in addition to cemented carbide containing tungsten carbide (WC) and cobalt (Co). Ceramics made of silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof, cubic boron nitride sintered body, diamond sintered body, hard phase made of polycrystalline diamond or cubic boron nitride, ceramics and iron group It is also possible to use an ultra-high pressure fired body in which a binder phase such as metal is fired under ultra-high pressure.
The tool body (1) and the shank portion according to Example 1 of the present invention are manufactured from a cemented carbide using, for example, an alloy tool steel such as SKD61 and the tool body (1) as an alloy tool steel such as SKD61. It is also possible to use a carbide shank type in which the shank portion is joined to the tool body (1).

According to the cutting edge exchange type rotary cutting tool and insert of the present invention, in addition to the finish dimensional accuracy of the bottom surface of the work material, the dimensional accuracy in vertical side surface finishing can be improved.

DESCRIPTION OF SYMBOLS 1 Tool body 2 Tip part 3 Mounting seat 4 Cutting edge part 5 Insert 6 Cutting edge exchange type radius end mill (Cutting edge exchange type rotary cutting tool)
7 Insert fitting groove 8 Fixing screw 9 Peripheral cutting edge 10 Rake face of outer peripheral cutting edge 11 Bottom cutting edge 12 Rake face of bottom cutting edge 13 Corner R cutting edge 14 Rake face of corner R cutting edge 15 Chamfering faces 16, 17 Chip discharge groove A Predetermined point on corner R cutting edge Ar1, Ar2 Axial rake angle (axial rake)
C Rotation center axis O Arc center point P, Q Boundary point Pr Reference plane VL Virtual straight line VS Virtual plane δ Radial rake angle (true rake angle)
ε Twist angle θ Radiation angle

Claims

A cutting edge exchange type rotary cutting tool (6) in which an insert (5) having a cutting edge (4) is detachably attached to a mounting seat (3) provided at a tip (2) of a tool body (1). And
The mounting seat (3)
A slit-like insert fitting groove formed in the distal end portion (2) of the tool body (1) so as to extend in the radial direction perpendicular to the rotation center axis (C) including the rotation center axis (C) of the tool. (7) and
A fixing screw (8) for fixing the insert (5) inserted in the insert fitting groove (7),
The cutting edge (4) of the insert (5)
An outer peripheral cutting edge (9) extending along the rotation center axis (C) direction;
A rake face (10) of the outer peripheral cutting edge (9);
A bottom cutting edge (11) extending along the radial direction;
A rake face (12) of the bottom cutting edge (11);
The radially outer end of the bottom cutting edge (11) and the distal end of the outer peripheral cutting edge (9) in the direction of the rotation center axis (C) are connected to the outer peripheral side of the distal end of the tool body (1). Corner R cutting edge (13) formed in a circular arc shape that is convex,
A rake face (14) of the corner R cutting edge (13);
A chamfered surface (15) including a rake face (14) of the corner R cutting edge (13) and a rake face (12) of the bottom cutting edge (11) at least a portion located outside in the radial direction; ,
A chip discharge groove (16) formed on the base end side of the rake face (12) of the bottom cutting edge (11) in the direction of the rotation center axis (C);
A chip discharge groove (17) formed inside the radial direction of the rake face (10) of the outer peripheral cutting edge (9),
The twist angle (ε) of the outer peripheral cutting edge (9) has a positive value,
The axial rake angle (Ar1) of the corner R cutting edge (Ar) at the boundary point (Q) between the corner R cutting edge (13) and the outer peripheral cutting edge (9) has a negative value,
The axial rake angle (Ar2) of the corner R cutting edge (13) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) has a negative value,
An arc of the corner R cutting edge (13) that is perpendicular to a reference point (Pr) including a predetermined point (A) on the corner R cutting edge (13) and the rotation center axis (C). Rake of the corner R cutting edge (13) with respect to the reference plane (Pr) in a virtual plane (VS) including a virtual straight line (VL) passing through a center point (O) and the predetermined point (A) The true rake angle, which is the angle at which the surface (14) is inclined, is defined as the radial rake angle (δ),
The radial rake angle (δ) of the corner R cutting edge (13) has a negative value over the entire cutting edge length of the corner R cutting edge (13),
The radial rake angle (δ) has a minimum value in an intermediate portion located between the pair of boundary points (P, Q) in the corner R cutting edge (13). Replaceable rotary cutting tool (6).
It is a blade-tip-exchange-type rotary cutting tool (6) according to claim 1,
The radial rake angle (δ) of the corner R cutting edge (13) at the boundary point (P) between the corner R cutting edge (13) and the bottom cutting edge (11) is the corner R cutting edge (13 ) And the outer peripheral cutting edge (9) at a boundary point (Q) smaller than the radial rake angle (δ) of the corner R cutting edge (13) (6) ).
It is a blade-tip-exchange-type rotary cutting tool (6) according to claim 1 or 2,
An angle at which the virtual straight line (VL) projected onto the reference plane (Pr) is inclined with respect to the rotation center axis (C) in the reference plane (Pr) is defined as a radiation angle (θ). ,
Cutting edge characterized in that the minimum value of the radial rake angle (δ) is set in the range of 5 ° to 50 ° in the radial angle (θ) of the corner R cutting edge (13). Replaceable rotary cutting tool (6).
An insert (5) used for the cutting edge exchange type rotary cutting tool (6) according to any one of claims 1 to 3.